A. Field
This invention relates to the art of audio (telephone) conferencing methods and systems, and more particularly to a method for adaptive mixing of audio signals during an audio conference which takes into account the geographic location of one or more of the participants.
B. Related art
A variety of network-based audio conferencing systems are known in the art and available in the marketplace. Such systems allow a plurality of distributed conference participants to hear each other during the course of a telephone conference. Such systems use a network platform or conference server that receives audio signals from the participants, mixes them and sends a mixed audio signal to the participants.
The following patent documents disclose network-based audio conference systems and components thereof: Christofferson, et al., U.S. Pat. No. 7,006,616; O'Malley et al., U.S. Pat. No. 7,054,424; McClennon et al., U.S. Pat. No. 6,408,327; O'Malley et al., U.S. Pat. No. 6,721,411; Baxley et al., U.S. Pat. No. 6,879,565; Potekhin et al., U.S. Pat. No. 7,054,820 and Chu et al., U.S. Pat. No. 6,683,858. The content of these references is incorporated by reference herein. These and other systems include a mixing unit, sometimes referred to in the art as a multi-point control unit or “MCU”, which mixes selected input audio signals to form an output audio stream for distribution to the telephones of the conference participants.
It is known in the art to provide mute and volume control features on telephone units to control transmission and reception of the audio streams to and from a telephone. The mute feature is typically implemented by pushing a mute button on a phone or pressing a particular digit sequence, such as the # or * key. When this feature is activated, the phone does not transmit audio signals to the MCU. The volume control features are also typically implemented locally on the phone by activating a dial or switch to increase or decrease the volume of the received (mixed) audio stream.
Sometimes audio conferences occur in which two or more conference participants are at the same location, e.g., in the same office, but are speaking on different phones. This situation can arise in a variety of contexts, including a situation where the participants are using cellular telephones and the conference is impromptu, i.e., the parties are not in a location where there is a land-line phone with speaker-phone capability. In this situation, the participants at the same location experience the effect of hearing the other co-located participants both directly (by virtue of being next to them) and over the phone. When this occurs, the co-located participants experience undesirable delay or echo between the speech produced locally and the speech emanating from the speakers in their phones. Furthermore, if the co-located participants were to attempt to solve the echo problem by activating a mute feature on their phone, then the non-co-located participants would not be able to hear what they were saying. If they turned down the volume, on their handset, then they would not be able to hear the non-co-located participants. Accordingly, there is no ready solution to this problem.
The methods of this disclosure correct this situation in a novel fashion by adapting the mixing of audio signals in the conference server in a manner which takes into account location of the participants.